Apparatus for separating solid materials of different specific gravities



Mar. 27, 1923.

M. HOKANSON.

APPARATUS FOR SEPARATING SOLID MATERIALS OF DIFFERENT SPECIFICGBAVITIES.

2 SHEETS-Emil l.

ORIGINALFILED JULY 17, 1918- /9 FIE.1.

INVENTOR WITNESSES Mar. 27, 1923. 1,449,604. M. HOKANSON.

APPARATUS FOR SEPARAHNG SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIES.

ORIGlNALHLED JULY 17, 1918- 2 SHEETSSHEET 2.

FISH;

WITNESSES wzsrww. 9 64 m Patented Mar. 27, 1923.

UNITED STATES PATENT OFFICE.

MARTIN HOKANSON, OF DULUTH, MINNESOTA.

APPARATUS FOR SEPARATING SOLID MATERIALS OF DIFFERENT SPECIFICGRAVITIES.

Application filed July 17, 1918, Serial No. 245,296. Renewed June 29,1922. Serial 1T0. 571,794.

To all whom it may concern:

Be it known that I, MARTIN HOKANSON, a resident of Duluth, in the countyof St. Louis and State of Minnesota, have invented a new and usefulImprovement in Apparatus for Separating Solid Materials of DifferentSpecific Gravities, of which the following is a specification.

This invention relates to apparatus for separating and concentratingsolid granular materials of different characteristics. One purpose ofthe invention is to provide apparatus for separating the valuable partof ore from gangue, by Sub ecting the material, in a finely crushedcondition, to the action of an upwardly flowing current of Water in aseries of vertical chambers, and controlling the water flow so that itsvelocity in each chamber is just sufiicient to carry therethrough theparticles of a particular material, the velocit in the next highercylinder not being su cient to carry the sa1d heavier particlestherethrough, but sufficient to carry the next lighter particlestherethrough. That is, each cylinder has a velocity which will notsupport granular solid material which has been carried through thepreceding cylinder. Consequently, at the top of each cyl nder theheaviest particles of material carrled therethrough are dropped out ofthe upwardly flowing stream, the other particles being carried onthrough the next cylmder, the heaviest particles of the remainingmixture being separated out at the top thereof, and so on.

Fig. 1 shows a vertical central section through the apparatus(diagrammatic) Fig. 2 shows a horizontal sectlon on the line 2-2 of Fig.1; Fig. 3 shows a partial vertical section on an enlarged scale of aportion of the apparatus shown in Fig. 1; Fig. 4 shows a modification ofthe feed arrangement; and Figs. 5 and 6 show modifications of asupplementary water supply system. I

If particles of matter of the same sizes but different weights areexposed to an upward flow of water of decreasing velocity, lightparticles will be carried farther than heavy particles, and the distanceto Wh1(ll the individual particles are transported will vary quiteaccurately accordin to their respective specific gravities. somewhatsimilar principle is that particles of matter of the same specificgravity, but of different sizes, will be graded by an upward current ofwater of decreasing velocity, the smaller particles being carried to thegreater distance. This principle has been applied to the grading ofsand. In the present case, the first of these principles only is used,namely, an upward current of water is applied to a mixture in which theparticles are all substantially of the same size but are of differentspecific gravities.

The present apparatus is particularly concerned with the separation ofthe gangue, such as silica, alumina, etc., from iron and other ores. Thesilica sometimes occurs in a coarse sandy state, sometimes in a veryfinely divided state, in some forms of ores being so fine that it isnecessary to crush the ore so that it will pass a one hundred meshsieve, or smaller, before the silica particles, etc), will be detachedfrom the iron oxide particles. The ordinary hematite ore when free fromsilica, has a specific gravity of about two to three. The silicaparticles having a specific gravity of somewhat less and the alumina isstill lighter. Therefore, when particles of ore, and particles ofgangue, etc., of the same size are subjected to a vertical current ofwater, the particles of gangue will be raised by a current of lesservelocity than that required to carry the particles of ore, and thisfurnishes a very accurate means for separating the one from the other.

It is a known principle that water moving through a pipe under pressureattains its greatest velocity at the center of the pipe, and that nearthe walls of the pipe the rate of flow is considerably less than at thecenter. Where a current of water in a pipe is carrying a mixture ofuniformly sized particles, there is a tendency for the heavier particlesto be thrown outward toward the walls of the pipe into the slowercurrent, and if the particles are of the same specific gravity,

but different sizes, the larger particles will be thrown out first.

In th'e practice of the present invention, iron ore, (or other ores ormaterials to be subjected to concentration as herein described) iscrushed, if necessary, to reduce it to sufliciently small particles tofree the gangue, resulting in a loose mechanical mixture. The mixture isgraded into sizes, the number of grades depending upon #tlre nature ofthe material being handled. Each grade is then subjected to separationaccording to this invention.

The graded mixture of ore and gangue and water is supplied to 'areceptacle 1, from which it is introduced to the bottom of a verticalcylinder 2, the first of a series of similar separators. It will beunderstood that the mixture of anular materials and water must be forceupward through the apparatus under ressure. This may be done bysituating t e mixing receptacle 1 at a height greater than that of theseparating apparatus, and connecting the bottom of cylinder 2 to it by api e 3. In this case the feeding is done entire y by gravity and isautomatic so long as the tank 1 is properly supplied. Instead of thisgravity feedin arrangement I mayuse a force pump, an carry the mixturefrom any convenient point. A desirable modification of the feeding meansis illustrated in Fig. 4, and described below.

The pipe 3 has avertical extension 4 connected to an inverted conicalportion 5, forming the lower end of cylinder 2. This first cylinder isof such length as to subject the mixture to the separating influence ofthe upward flowing current for suficient time to throw the heavyparticles to the outside. This cylinder forms a chamber A.

Surrounding theupper end of cylinder 2 is an enlarged casing or jacket6, the lower end of which is supported by the cylinder 2, and the upperend of which forms an aligned vertical cylinder 7. Thus an enlargedchamber B is formed around the upper end of cylinder 2, and below this,and surrounding the cylinder is an annular gocket, C. The cylinder 7forms a chamber which in turn leads into an enlarged chamber E, formedby a casing or jacket 8, surroundin the upper end of cylinder 7 andsupported t ereby just as the casin 6 surrounds and is supported by thecylmder 2. The casing 8 forms an annular pocket F about the to ofcylinder 7, and extends upward as a t ird vertical aligned cylinder 9,

forming the cylindrical chamber G. The

upper end of this third cylinder is surrounded by an enlarged circulartank 10, which forms an overflow basin H, around the upper end ofcylinder 9.

The bottom 11 of the annular pocket C formed by the junction of easing 6and cylinder 2 13 provided with perforations 12. Fitted into theseperforations are nozzles 13 having their upper ends flush with thebottom 11 and their lower ends curved and pointing in the direction ofinclination of the bottom 14 of a draw-off chamber I which is situatedimmediately beneath the perforated bottom 11. 'The bottom 14 and wallsof the chamber I are inclined in each direcinaaeoe tion around thechamber A so that said chamber I increases in size to the point Where itempties into a draw-oii port 15, which leads b a suitable pipe 16 to anydesired point. lsirectly opposite the draw-off port 15, and at thesmallest part of the chamber I, is an inlet port 17, to which isconnected a pipe 18 controlled by valve 19.

The same arrangement of draw-oif chamber, perforated bottom, and inletand outlet ports therefor are provided at the junction of casing 8 andcylinder 7, as illustrated in the drawing, and indicated by similarreference numerals having the letter It added, except for the annulardraw oflt' compartment marked J.

The overflow compartment H is provided with a suitable drain pipe 20.

It will be understood that the pipes 16, 16, and 20 are'led to anysuitable place for discharge of the material, and are provided pith thenecessary valved connections there- In a former application Serial No.207,- 001, filed December 13, 1917, I have described apparatus somewhatsimilar to this, and having similar objects, in which each of thesucceeding cylindrical chambers corresponding to A, D, and C, is largerthan its preceding cylinder. This was for the purpose of securing adecreased flow of liquid in each succeeding cylinder, so as to cause thethrowing out of the heavier particles at the top of the first cylinder,and so on. I have found, however, thatwith certain mixtures, andmaterials of certain composition, a sufiicient quantity of water isdrawn off around the top of the first cylinder 2, to secure thenecessary decrease of velocity in the cylinder 7, for the purpose ofseparation. In theory, the apparatus is designed so that the heaviestparticles will be just barely carried to the top of the chamber A, bythe velocity of flow therein, and

y will be thrown out into theienlar ed chamber B, fallin into the pocketand removed throug li draw-off chamber I and pipe 16. Now, a certainamount of water is carried off with the heavier particles with thisoperation, and consequently the volume of water flowing upward throughchamber D is less than that in chamber A. Since, theoretically, thevelocity of chamber D should be just sufiicient to raise the particlesof next greatest specific gravity to-the top of that chamber, it isessential that the velocity of flow in chamber D be less than in chamberA, but still it must be great enough to raise the second class ofparticles to the top there of. In order to compensate for the loss ofwater about the top of the first cylinder, I find that the secondcylinder must often be as small as the first, or even smaller, in orderto maintain the desired velocity therein. Consequently, in thisapparatus, the succeeding cylinders are not necessarily larger, but maybe made of approximately the same size, or of even smaller sizesuccessively, according to the circumstances and materials of each case.

It is necessary to accurately measure the comparative specific gravitiesof the materials being separated, to determine the proportion of eachconstituent of the mixture, and to regulate carefully the velocities inthe several cylinders in order to give the required velocities in theseveral cylinders to secure an eflicient separation.

For this purpose I prefer to provide cylinders of approximately the samesize, and regulate the velocities of flow in each one by means ofcontrolling the amount of water drawn off between cylinders.

This is done by means of valves 21 and 21 in the draw-01f pipes 16 and16, and by supplying additional water to the draw-off compartments I andJ by means of the pipes 18 and 18*. Manifestly, the rate of escape ofwater through the ports '12 and 12 is dependent upon the discharge ofwater from the compartments I and J. If the water introduced from theorts 18 and 18 is equal to the amount owing out the pipes 15 and 15*,then there can be no escape through 12 and 12*. Consequently, thesesupplementary supplies of water must be so regulated as to accuratelycontrol the discharge from the concentrating apparatus at each draw-offpoint. By this means, the velocity of flow in each of the chambers A andD can be accurately regulated, and varied to suit the proportions andweights of the materials being separated.

The operation of the apparatus is as follows: Any kind of ore from whichthe gangue is to be separated (or other mechanical mixture of finematerials of different specific gravities) is crushed and accuratelygraded to a uniform size. The required size varies according to thenature of the ore or other material to be separated. The graded mixtureis then placed in the receptacle, 1, and mixed with water to carry it.This mixture flows by gravity through pipe 3 and upward through cylinder2. The particles of greatest specific gravity will be thrown to theoutside of the chamber A as the mixture passes therethrough, and uponreachin the enlarged chamber B, the heavier particles at the outside ofthe stream will be thrown outward. The rate of flow being suddenlydecreased, the upward stream will not be sufficient to support the heavyparticles and they fall into the annular chamber C, settle to the bot.-tom thereof and escape through the nozzles 13 into the draw-off chamberI and through the pipe 16. The constant outflow from the bottom ofchamber C produces a slight downward current in said chamber, whichassists in leading the heavy particles into said chamber and down, tothe discharge orifices. The amount of Water, and the size of thechambers B and D are so related that all but the heaviest particles arecarried on upward throu h the cylinder 7 and into the chamber Here againthe heavier particles are no longer supported by the flow of water andfall outward around the top of cylinder 7 into the pocket F, and aredrawn off just as above described. The very light material is againcarried'on through the cylinder 9, and finally flows off by Way of pipe20 to be discharged at any suitable place. Or a third separatingarrangement can be used to clean the Water, so that it may be used overagain, as in localities where water is scarce.

In my prior application above referred to I show a centrifugal pump forforcing the mixture through the separating apparatus. The mixture of oreand water has a'rapid wearing effect on the pump casing, and therefore Iprefer to use the gravity feed above described. However, in some cases apump feed may be desirable. By providing a tank 30, (Fig. 3) adapted toreceive the mixture of ore and water, and connecting it to the bottom ofcylinder 2 by a pipe 31, and leading a horizontalbranch 32 into the pipe31, water may be pumped into the apparatus so as to give sufficientpressure and velocity to the mixture, regardless of the elevation ofmixing tank 30. Any form of pump may be used, though I have illustrateda centrifugal pump 33.

In this modification it is better to introduce water from pump 33 in theform of a jet under high pressure, to get an injector action. To thisend pipes 31 and 32 are reduced in size toward their meeting ends and aninterior nozzle '34 is ledinto pipe 32 from pump The end of this nozzleextends nearly to the restricted portion lying at the junction of pipes31 and 32. Consequently, the stream of clear water from nozzle 34 willcarry the mixture from tank 30 into pipe 31 and into the separatingapparatus, under suflicient pressure to move it through the apparatus.

In order to keep the mixture of Water and solid particles in tank 30uniform, I may provide an agitator, comprising a vertical shaft 35having lateral paddles 36 thereon, in the tank. This may be driven byany suitable means, such as by belt pulleys 51,

or operated intermittently by hand.

In order to supply water and solids in proper porportions I' provide awater supply pipe 50 having a control valve 37, and a granular supplypipe 38, having a control gate 39 therein.

In Figs. 5 and 6, I show modifications of the supplementary water supplymeans.

In Fig. 5, a water pipe controlled by valve 41 leads into the enlargedcasings 6 just above the top of cylinder 2, and is connected to anannular ipe 42 extending around the chamber l as shown. The underside ofpipe 42 is perforated, as shown, so that Water therefrom is forceddownward, thus aiding the separating current above described in leadingthe heavy particles into chamber C. A similar arrangement may beprovided for chamber E.

Near the bottom 11 of chamber C another pipe 43 having a control valve44, leads through the casing to a circular perforated pipe 45 in chamberC. The perforations in pipe 45 are on the lower side thereof and aresituated respectively just above nozzles 13, so as to aid in driving outthe solids therethrough. A similar arrangement may be provided forchamber F.

Instead of placing pipe 42 inside the chamber B, I'may make an offset 45in the wall of casing 6, as shown in Fig. 6, and place pipe 42 on theoutside and lead small nipples 46 to the inside of chamber B.

Any desired combination of these modified features may be provided andused. Or they may all be attached to a standard apparatus, and used ornot according to the particular circumstances of each case.

It will be obvious that the means pro-' vided allow ver accurateadjustment of the rate of flow in each chamber.

It will be understood that the drawings are merely illustrative of myapparatus, and the proportions of the various compartments are notintended to be fixed by the dimensions shown. For instance, the cylinder7 may be longer than the cylinder 2, if desired, and larger or smallerin diameter than that cylinder. Likewise, the cylinder 9, which is hereshown as very short, and in efiect merely an outlet from chamber E, maybe prolonged, and provided with draw-0d connections and. compartmentssimilar to those about the tops of cylinders 2 and 7 The apparatus isnot limited to the separation of iron ore, but may be used for anymixture of ore and gangue, or in fact for any mechanical mixture ofparticles of different specific gravities, where the difference inspecific gravities is large, and the size of the particles the same, ornearly so.

The method carried out by the above described process is not claimedherein but is claimed in my application Serial No.

272,327, filed Jan. 21, 1919.

I claim:

1. Apparatus for separating solid granular materials, comprising avertical vessel, means for forcing the materials in a finely dividedform mixed with water upwardly through said vessel, said vesselintermediate its height being provided with a portion of increasingdiameter providing an annular maaeoa chamber in which the solids aredeposited by radial separation from the vertical stream, sa d annularenlargement being provided w1th a series of outlets uniformly spacedaround said vessel, an annular chamber receiving from said dischargeopenings, said annular chamber being or progressively increasmgdimensions from one side, and a controllable outlet from the largestpoint of said draw-01f chamber.

2. Apparatus for separating solid granu-' lar materials, comprising avertical vessel, means for forcing the materials in a finely dividedform mixed with water upwardly through said vessel, said vesselintermediate its height being provided with a portion of increasingdiameter providing an annular chamber in which the solids are depositedby radial separation from the vertical stream, said annular enlargementbeing provided with a series of outlets uniformly spaced around saidvessel, means for regulating the amount of water drawn off through saiddischarge openings, and means to introduce an additional supply 'ofwater to said vessel adjacent the withdrawal point.

3. Apparatus for separating solid granular materials, comprising avertical vessel, means for forcing the materials in a finely dividedform mixed with water upwardly through said vessel, said vesselintermediate its height being provided with a portion of increasingdiameter providing an annular chamber in which the solids are depositedby radial separation from the vertical stream, said annular enlargementbeing provided with a series of outlets uniformly spaced around saidvessel, an annular draw-off chamber receiving from said openings andbeing of progressively increasing dimension from one side, a withdrawaloutlet from the largest point of said draw-off chamber, and anadditional water supply connected to said draw-0d chamber.

4:. Apparatus for separating solid granular, materials, comprising a.vertical vessel, means for forcing the materials in a finely dividedform mixed with water upwardly through said vessel, said vesselintermediate its height being provided with a portion of increasingdiameter providing an annular chamber in which the solids are depositedby radial separation from the vertical stream, said annular enlargementbeing provided with a series of outlets uniformly spaced around saidvessel, an annular drawofi' chamber receiving from said dischargeopenings and being of increasing dimensions from one side, an outlet atthe largest point of said draw-ofi' chamber, and means for introducingan additional water supply adjacent to said draw-ofi' openings and sorelated thereto as to induce a current through said draw-off openings.

5. Apparatus for separating solid granular materials, comprising avertical vessel, means for forcing the material in a finely divided formmixed with water upwardly through said vessel, said vessel intermediateits height being provided with a portion of increasm diameter providingan annular chamber in which the solids are deposited by radialseparation from the vertical stream, said annular enlargement beingprovided with a series of outlets uniformly spaced around said vessel,an annular drawofi chamber receivin from said discharge openings andbeing 0% progressively-increasing dimension from one side, a dischargeoutlet from the largest point of saiddrawoff chamber, and nozzles insaid discharge openings projecting into the draw-off chamber anddirected toward the dscharge opening therefrom.

6. Apparatus for separating solid granular materials, comprising avertical vessel, means for forcing the material in a finely divided formmixed with water upwardly through said vessel, said vessel intermediate.

its" height being provided with a portion of increasing diameterproviding an annular chamber in which the solids are deposited by radialseparation from the vertical stream, said annular enlargement beingprovided with a series of outlets uniformly spaced around said vessel,an annular drawoif chamber receiving from said discharge openings andbeing of progressively increasing dimension from one side, a dischargeoutlet-from the largest point of said draw-off chamber, nozzles in saiddischarge openings projecting into the draw-ofi' chamber and directedtoward the discharge opening therefrom, and a water supply connected tosaid draw-off chamber and directing the current in the direction of thenozzles.

7. Apparatus for separating solid granular materials, comprising avertical vessel,

means for forcing the materials in a finely divided form mixed withwater upwardly through said vessel, said vessel intermediate its heightbeing provided with a portion of increasing diameter providing anannular chamber in which the solids are. deposited by radial separationfrom the vertical stream, said annular enlargement being provided with aseries of outlets uniformly spaced around said vessel an annulardraw-ofi chamber receiving from said openings and being of progressivelyincreasing dimension from one side, a withdrawal outlet from the largestpoint of said draw-off chamber, an additional water sup 1y connected tosaid draw-off chamber, and further water supply to the upper portion ofsaid annular enlargement.

3 8. Apparatus for separating solid granular materials, com rising avertical vessel, means for forcing t e material in a finely divided formmixed with water upwardly through said vessel, said vessel ntermediateats heightbe ng provided with a portion of mcreasm diameter providing anannular chamber-in which the solids are deposited by radial separationfrom the vertical stream, said annular enlargement being provided witha". series of outlets uniformly spaced around said vessel, an annulardraw-oft said draw-off openings and so related thereto as to induce acurrent through said drawofi openings, and a further water sup ly to theupper portion of said annular enlargement.-

9. Apparatus for separating solid granular materials, comprising avertical cylindrical vessel, means for-forcing the material in a finelydivided form mixed with water upwardly through said vessel, a secondvessel above the first vessel and having its lower end extending belowand of larger diameter than the top ofthe first vesel, thereby providingan annular chamber in which the solids are deposited by radialseparation from said annular chamber being provided with a series ofoutlets uniformly spaced around the vertical stream, the upper end ofthe first vessel curving progressively outwardly,

said vessel, an annular chamber receiving A from said dischargeopenings, said annular chamber being of progressively increasingdimensions from one side, and a controllable outlet from the largestpoint of said drawofi' chamber.

10. Apparatus for separating solid granular materials, comprising avertical cylindrical vessel, means for forcing the material in a finelydivided form mixed with water upwardly through said vessel, a secondvessel above the first vessel and having its lower end extending belowand of larger diameter than the top of the first vessel, therebyproviding an annular chamber in which the sol-v terials to be separatedto the bottom of the said cylinder, a casing surrounding the top of thesaid cylinder and attached to the outer wall thereof below thetop,drawwfi ports at the junction of the casing and cylinder wall, means toregulate the amount of water drawn from the apparatus through saidports, means to introduce a re ated amount of water above said draw-oand a second cylinder leading upward from the said casing.

12. Apparatus for separatmg granular materials of different characteristcs, comprising a storage receptacle for a mixture of water and thegranular materials, means to force the mixture from the storagereceptacle to the bottom of a vertical cylinder, an enlarged casingabout the top of the said cylinder, means to draw off solid materlaldeposited in said casing at the top of the first cylinder, means toregulate the amount of water drawn off with said solid material, meansto introduce a supplementary supply of water to said casing, and aseries of succeeding axially aligned cylinders and casings havingsimilar drawing off and water supplying means.

13. Apparatus for separating a mixture of solids of differentcharacteristics, comprising a vertical cylinder, means to introduce themixture in a stream of water to the bottom of the cylinder, an enlargedcasing about the top of the cylinder and connected to the outer wallthereof below the top, perforations in the casing wall at its bottom, anannular chamber surrounding the connections between the casing and thecylinder wall, an escape port from the draw-off cham ber, and a valvedinlet pipe thereto connected to a water supply.

14. Apparatus for separating granular materials of differentcharacteristics, comprising a series of vertically arranged cylindershaving enlarged chambers about the top of each cylinder, means to drawofi' granular material from each enlarged chamber, and means to supplyadditional water at each draw-oft level to compensate for that drawn offwith the granular material.

15. Apparatus for separating granular materials of differentcharacteristics, comprising a series of vertically-arranged upward-flowcylinders, an enlarged settlement chamber connecting each cylinder tothe cylinder next above, a series of perforations in the bottoms of saidsettlement chambers adapted to carry off granular material depositedthere, an annular draw-off chamber beneath each settlement chamber andconnected thereto by said perforations, an outlet from said draw-offchamber tocarry off granular material and water and an inlet thereto tosupply water to compensate for the water discharged from the draw-offchamber.

16. Apparatus for separating granular materials of differentcharacteristics, comprising a series of vertically-arranged upward-flowcylinders, an enlarged settlement ports,

chamber connecting each cylinder to the cylinder next above, a series ofperforations in the bottoms of said settlement chambers adapted to carryoff ranular material deposited there, an annu ar draw-ofi chamberbeneath each settlement chamber and connected thereto by saidperforations, an outlet from said draw-oil chamber to carry off granularmaterial and water, an inlet thereto to supply water to compensate forthe water discharged from the draw-ofi chamber, and means to control theamount of water supplied to the draw-off chamber.

17. Apparatus for separating solidmaterials comprisin in combination, avertical casing, a second casing above the said first casing and havingits lower end of larger diameter than the top of the first casing andextending below the top of the first casing and forming an annularchamber therearound, means for forcing the material in a finely dividedform mixed with water upwardly through said casings, and a con- Iitantlyopen outlet from said annular cham- 18. Apparatus for separating solidmaterials comprising in combination, a vertical casing, a second casingabove the said first casing and having its lower end of larger diameterthan the top of the first casing and extending below the top of thefirst casing and forming an annular chamber therearound, means forforcing the material in a finely divided form mixed with water upwardlythrough said casings, and a series of constantly open withdrawalopenings in the bottom of said annular chamber and entirely around thesame.

19. Apparatus for separating solid materials comprising in combination,a vertical casing, a second casing above the said first casing andhaving its lower end of larger diameter than the top of the first casingand extending below the top of the first casing and forming an annularchamber therearound, means for forcing the material in a finely dividedform mixed with water upwardly through said casings, the bottom of saidannular chamber being provided with a series of withdrawal openingsextending entirely around the same, an annular withdrawal chamber belowsaid perforated bottom and receiving the discharge from said openings,and a constantly open draw-ofi' outlet from said last named chamber.

20. Apparatus for separating solid materials comprising in combination,a vertical casing, a second casing above the said first casing andhaving its lower end of larger diameter than the topof the first casingand extending below the top of the first casing and forming an annularchamber therearound, the bottom of said annular chamber being providedwith a series of withdrawal openings extending entirely around the same,means for forcing the material in a finely divided form mixed with waterupwardly throu h said casings, an annular draw-off cham er below saidperforatedbottom andreceiving the discharge from said openings and beingof progressively increasing dimension from one side in both directionsto the other side, and an outlet from the largest point in the saiddraW-ofi' chamber.

21. Apparatus for separating solid materials comprisin in combination, avertical casing, a second casing above said first casing and having itslower end of larger diameter than the top of the first casing andextending below the top of the first casing and forming an annularchamber around the first casing,'a third casing above the second casingand having its lower end of larger diameter than the top of the secondcasing and extendin below the top of the second casing and orming anannular chamber therearound, means for forcing the material in a finelydivided formmixed with water upwardly throu h said casings, andconstantly open oufiets from both of said annular chambers.

22. Apparatus for separating solid materials comprising in combination,a vertical casing, a second casing above the said first casing andhaving its lower end of larger diameter than the top of the first casingand extending below the top of the first casin and forming an annularchamber aroun the first casing, a third casing above the second casingand having its lower end of larger diameter than the top of the secondcasing and extending below the top of the second casing and forming anannular chamber therearound, means for forcing the material in a finelydivided form mixed with water upwardly through said casings, the bottomsof each of said annular chambers being provided with discharge openingsextending entirely around the same, an annular withdrawal chamber beloweach of said perforated bottoms and receiving the discharge therethroughand being of progressively increasing dimension from one side in bothdirections to the other side, and a draw-off outlet from the largestpoint of each of said draw-off annular chambers.

In testimony whereof, I have hereunto set my hand.

MARTIN HOKANSON.

